1. Field of the Invention
The present invention relates to a conveyance direction changing device for changing a conveyance direction of a photosensitive material in an automatic developing apparatus for developing the photosensitive material such as a photographic film and a photographic paper.
2. Description of the Related Art
In an automatic developing apparatus in which a variety of development solutions including a liquid developer, a liquid fixer and a liquid stabilizer are filled in treatment tanks and photosensitive materials are successively conveyed into the development solutions in the treatment tanks, racks are suspended in the respective treatment tanks and the photosensitive materials are conveyed in these racks.
Each rack is provided with a conveying device for the photosensitive material. The photosensitive material is conveyed, face down, by the conveying device and the photosensitive material has its conveyance direction changed by 180.degree. using a conveyance direction changing mechanism provided at a bottom part of the rack so that the photosensitive material can be conveyed face up.
A known conveyance direction changing mechanism is shown in FIG. 5. This mechanism is constructed such that feed rollers 31, 32, 33 are arranged in contact with the opposite sides and bottom of a turn roller 30 that is drivingly rotated. Arcuate guides 34 are provided between adjacent feed rollers 31, 32, 33. A photosensitive material A fed to a contact portion between the turn roller 30 and the feed roller 31 at one side has its conveyance direction changed by 180.degree. along a lower part of the outer surface of the turn roller 30 by the rotation of the turn roller 30 and the feed rollers 31, 32, 33.
Since the photosensitive material A is conveyed along the fixed guides 34 in the above conveyance direction changing mechanism, it is likely to be scratched by the contact with the guides 34. This presents a problem since the device sometimes does not provide good quality products.
In order to solve the above problem, a conveyance direction changing device having a small likelihood of scratching the photosensitive material was proposed in Japanese Unexamined Patent Publication No. 8-339071. FIG. 6 shows the conveyance direction changing device disclosed in the above mentioned publication. This device is constructed such that an endless belt 41 having a portion thereof held in contact with a lower part of the outer surface of a turn roller 40, rotated in one direction, is moved in a direction of the arrow at the same speed as the circumferential speed of the turn roller 40. This conveys a photosensitive material A fed between a contact portion, between the belt 41 and the turn roller 40, in a circumferential direction of the turn roller 40 while being tightly held between the turn roller 40 and the belt 41.
Since the photosensitive material A is tightly held between the turn roller 40 and the belt 41 in the above conveyance direction changing device, it is possible to have its conveyance direction changed without damaging the photosensitive material.
In the above device, the turn roller 40 and a plurality of belt rollers 42 for guiding the movement of the belt 41 are not necessarily precise rollers having an outer diameter uniform over the entire length. With the use of imprecisely dimensioned rollers or a mounting error in the location of the rollers, the belt 41 cannot be brought into even contact with the turn roller 40 over the entire width.
Here, if the contact pressure between the turn roller 40 and the belt 41 is uneven along the widthwise direction of the belt 41, the photosensitive material A that is conveyed while being tightly held between the turn roller 40 and the belt 41 slips in positions where the contact pressure is low. As a result, the photosensitive material A moves in a zigzag manner and the side edges thereof may be strongly brought into contact with side guides for guiding the movement of the side edges of the photosensitive material A, thereby being scratched. This disadvantageously results in a considerable reduction in product value.
It is an object of the present invention to change the conveyance direction of a photosensitive material without causing it to move in a zigzag manner in a changing device while tightly holding it between a turn roller and a belt.